void main(List<String> args){
  PayBase wx=Wxpay();
  wx.pay();
  PayBase ali=Alipay();
  ali.pay();

}
abstract class PayBase{
  void pay();
}
class Wxpay implements PayBase{
  @override
  void pay(){
    print("微信支付");
  }
}
class Alipay implements PayBase{
  @override
  void pay(){
    print("支付宝支付");
  }
}